A conventional can body maker apparatus is disclosed in U.S. Pat. No. 3,696,659, issued to J. H. Maytag and an improvement to the ram assembly of the can body maker ram assembly is disclosed in U.S. Pat. No. 4,934,169, issued to C. M. Grimes, et al. Both of these patents are assigned to Adolph Coors Company. An example of a conventional redraw system is also described in U.S. Pat. No. 3,735,629, issued to Elpidofor Paramonoff, and assigned to Standun Inc. The aforedescribed patents are incorporated herein by reference as if fully set forth. The assignee of the instant invention is also the assignee of co-pending application, "Improved Body Maker Apparatus," Ser. No. 899,201, which discloses a counterbalance mass system that improves the speed and efficiency of can body makers.
Can body makers produce elongated can bodies from shallow metal cups or can shells. The can shells have a wall thickness of approximately 0.009 to 0.012 inch, and the elongated can bodies have a wall thickness reduced to approximately 0.0045 inch. In a conventional can body maker apparatus, a ram is movably mounted for reciprocal, straight line motion at rates sufficient to form from between 180 and 220 can bodies per minute. The stroke length, that is the distance traveled by the movable ram, is between about 18 to 26 inches. As a general rule, for a given can body maker, the shorter the ram stroke, the greater the rate or number of cycles per minute at which the ram can be operated. Misalignment as small as between about 0.0005 and 0.0010 inch can result in the formation of defective cans. In conjunction with the reciprocal motion of the ram, a redraw sleeve is supported in a redraw assembly. The redraw sleeve engages the shell prior to contact by the ram, applying a restraining force against the shell as it is worked through a redraw die. The redraw process elongates the sidewalls of the can shell and decreases the sidewall thickness and overall diameter of the can shell. The redraw operation is followed by two or three ironing stations that further elongate and thin the walls of the can shell to form a one piece can body. Finally, the body maker can be equipped with a doming station that further forms the enclosed bottom of the can body into a desired structural configuration.
The redraw assembly operates at the same rate of reciprocation as the ram assembly. Mechanical linkage is provided between the main crank shaft of the can body maker and both the ram assembly and the redraw assembly. The specific linkage translating the motion of a cam mechanism into the linear straight line motion required by the redraw assembly includes a leader pin, redraw head, cam follower, idler arm, push rod, and an air spring/air cylinder, all of which are required to effect the reciprocal motion of a redraw sleeve carriage assembly. In order to minimize the potential for misalignment, in conventional body makers, the redraw sleeve carriage is supported on a track way that is parallel with the ram assembly. Needless to say, a significant amount of mass is being reciprocated in the redraw carriage assembly and this mass can contribute to the misalignment problem discussed above. A biasing system such as an air spring/air cylinder is in communication with the redraw assembly and supplies the force necessary to maintain the cam follower in contact with the cam mounted on the crank shaft. The air spring/air cylinder system is a complex assembly that includes an air cylinder, surge tank, and connecting hoses that require significant attention during operation and continuous maintenance.